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A novel method for extremum response estimation of wheel–rail rolling noise by the development of moving pseudo-excitation method

Zhu Zixu, Xu Qingyuan, Xu Lei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e160, 2023

EN

Wheel–rail rolling noise (WRRN) hold strong randomicity and time-varying time–frequency characteristics subjected to a moving vehicle on the tracks, consequently, its prediction highly depends on accurate simulation and calibration of vehicle–track interaction and noise source. In this work, a novel method is proposed to estimate the extreme value of WRRN. First, a flexible wheelset modeled by Timoshenko beam with variable cross sections is introduced and coupled into the rigid–flexible multi-body vehicle–track interaction model previously established by the finite elemental matrix coupling method. To simulate the noise source intensity and frequency characteristics, a moving pseudo–excitation method (MPEM) is developed for obtaining time-varying power spectral density (PSD) of system responses, and to obtain the extremum of time-domain response. Furthermore, a simplified WRRN prediction model (including the wheel, rail, and trackslab noise model), integrated with the modern acoustic theory, is presented to estimate the extremum of WRRN–sound pressure level (SPL). Numerical examples show the effectiveness and suitability of this model from aspects of system response amplitude, the PSD of wheel acceleration, the wheelset eigenfrequency distribution, the WRRN–SPL spectrum, and the extremum of WRRN–SPL. The practicality of the MPEM in predicting WRRN–SPL is also validated. The influence of vehicle speed and ground surface type on WRRN is investigated, and it shows that the vehicle speed is positively correlated to WRRN–SPL and the extremum of WRRN–SPL will be decreased by the reduction of the effective flow resistivity within bounds.

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A method for vehicle–track–soil interaction analysis considering soil deformation

Li Zheng, Xu Lei, Wang Weidong

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e210, 2022

EN

In this work, an engineering practical method is put forward to characterize the static and dynamic mapping relationship between soil deformation and its induced system performance. The main novelty lies in the achievement of mapping relationship analysis subject to arbitrary soil deformation-induced vehicle–track–soil (VTS) static geometric deformation and dynamic behavior. In this practical model, the increment and iteration methods are introduced and integrated into the static mapping analysis to solve the nonlinear interlayered contact and separation, and subsequently, to achieve dynamic mapping analysis under a VTS dynamics framework, besides, the Wavelet transform is applied to obtain the more distinct observation signal in the time domain. Apart from the discussion on the time domain, the analysis on the frequency domain is implemented in the numerical studies to further illustrate the influence of soil additional deformation from the dynamic mapping perspective. Moreover, the difference between the dynamic responses of the unit base plate and longitudinal connected base plate subject to different combination of wavelength and amplitude of soil deformation is analyzed.

3

Yarn Damage Evaluation in the Flat Knitting Process

Iqbal Waqar, Jiang Yaming, Qi Ye-xiong, Xu Lei

Autex Research Journal

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2021

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Vol. 21, no. 3

272--283

EN

Textile yarns are subjected to numerous types of forces during knitting, usually leading to yarn damages, such as decrease in tensile, bending, shearing, and surface properties, which are closely related to different yarn properties, knitted structures/actions, and machine settings. This article comprehensively evaluated yarn damages in the computerized flat knitting process. Five different commercially available and commonly used yarns including cotton, wool, polyester, acrylic, and viscose were selected as raw materials, and the tensile, bending, shear, and frictional properties were investigated and compared before knitting and after being unraveled from plain- and rib-knitted fabrics, respectively. The results show that knitting actions/structures exhibit different damage extents for all different raw materials. It has been observed that the modulus is declined by 3–30% for bending, 2–10% for tensile, and 8–80% for shearing due to flat knitting action, respectively. The frictional coefficient of yarns also increased from 6 to 23%. As compared to yarn before knitting, the yarns unroved from plain and rib structures have been damaged to a great extent as a result of the loss of mechanical properties. The results are completely in agreement with the statistical analysis that clearly represents the significant loss in yarn properties during the knitting process. The microscopic analysis of the yarns clearly illustrates the effect of knitting action on yarn surface and mechanical properties. For yarn’s cross-sectional shearing properties testing, this article self-designed an innovative “Yarn Shear Testing Device.” The methodology and results are of great importance for improving the quality of knitted products, evaluating knitting yarns’ knittability, and in the development of high-performance technical textiles.

4

Numerical simulation for train-track-bridge dynamic interaction considering damage constitutive relation of concrete tracks

Xu Lei, Yu Zhiwu, Shan Zhi

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

533--555

EN

In this work, a novel and practical method is developed to depict the track slab damage and residual strain evolution, where the concrete damage constitutive relation of track slabs is considered within the train–track–bridge dynamics framework. A three-step strain method is presented to judge the load/unloading, compression/tension status of track slab elements ergodically, so that the damage condition and residual strain of track slabs can be determined. To improve the computational accuracy and efficiency, the combination of the matrix augment method and iterative solution algorithm is elucidated in detail. To validate the present model, the solutions among incremental solution, iterative solution, and non-iterative solution are firstly illustrated, and then experimental studies are performed to declare the effectiveness of this model in characterising strain/stress relation of concrete no matter in compression state or in tension state, and finally, other model results are also introduced to prove the effectiveness of this model. In the numerical studies, the damage distributions of track slabs in the longitudinal and lateral direction are presented, where the influence of track irregularities and track slab positions on the bridge is clarified, besides, the evolution of the damage and residual strain of a track slab subject to a moving train is revealed.